Reading https://docs.microsoft.com/en-us/windows/win32/direct2d/comparing-direct2d-and-gdi :
Presentation Model
When Windows was first designed, there was insufficient memory to allow every window to be stored in its own bitmap. As a result, GDI always rendered logically directly to the screen, with various clipping regions applied to ensure that it did not render outside of its window. In contract, Direct2D follows a model where the application renders to a back-buffer and the result is atomically “flipped” when the application is done drawing. This allows Direct2D to handle animation scenarios much more fluidly that GDI can.
The author says Direct2D uses back-buffer and by 'flipped' he meant swap-chain I guess. I created a simple demo that draw a rectangle at random location on mouse click. But previous rectangles are not cleared so it seems that it is drawn directly to the screen and does not use any back-buffer.
